Railway Technology Newsletter No.53, December 18, 2015
315
World’s Largest Superconducting Flywheel Energy Storage System
Tomohisa YAMASHITA
Chief Researcher, Maglev Systems Technology Division
1. Introduction
RTRI has developed a superconducting flywheel energy
storage system (Fig.1). It has a large flywheel (4,000
kg with a diameter of 2 m) levitated by an innovative
superconducting magnetic bearing devised by RTRI.
This system is the world’s largest mechanical type of
energy storage system that can be discharged and
charged. The significant merit of this system is that it
implemented high-temperature superconducting technology at a commercial machinery level for sustaining
a superconducting state without using a refrigerant such
as liquid nitrogen.
2. Superconducting Flywheel Energy Storage System
A flywheel energy storage system works by converting
electric energy into the kinetic energy of a flywheel.
It can be charged by increasing the revolution speed,
and conversely, discharged by decreasing the revolution speed. One of the characteristics of this system
is that the flywheel size has been enlarged to raise its
output and capacity. Another characteristic is the use
of a superconducting magnetic bearing that can levitate
such a heavy object weighing about 4 tons and keep the
flywheel floated for a long period of time while minimizing
the loss of rotating energy. Maximum revolution speed
of this system is 6,000 rpm and its output is 300 kW. It
has an energy storage capacity of 100 kWh, indicating
that this is the largest superconducting
flywheel
energy
storage system in
the world.
3. Future Perspectives
While solar power
generation gives
clean and renewable
energy, it is difficult
to provide stable power generation. An objective of the
newly developed superconducting flywheel energy storage system is to realize smooth output of power generation by concurrently using solar power generation. It is
expected that this concept will facilitate stable power
supply from solar power generation to grid electricity.
Moreover, by installing our system in each electric
railway substation, the charging and discharging of the
regeneration canceled energy can be implemented,
thereby contributing to the improvement of the railway
energy efficiency.
The development of this system has been carried out
since FY 2012 and is subsidized by the New Energy
and Industrial Technology Development Organization.
Generator motor
by RTRI
CFRP flywheel
by Kubotek Corporation
Vacuum vessel
by Mirapro Co., Ltd.
System connection
with the solar power
plant by Public
Enterprise Bureau of
Yamanashi Prefecture
Fig.1 Superconducting Flywheel Energy Storage Unit
3
2 m in diameter
Superconducting
magnetic bearing
by RTRI and Furukawa
Electric Co., Ltd.